In multi-carrier systems, data is transmitted on multiple subcarriers and then collected at a receiver for the multi-carrier system. OFDM (orthogonal frequency division multiplexing) signals are used by some multi-carrier systems where transmitted data is modulated on a number of closely spaced orthogonal subcarriers. Further, some multi-carrier systems utilize standard transmission protocols to facilitate the detection and synchronization of received signals. For example, a preamble waveform can be used to precede or follow data transmissions to allow a receiver to synchronize to the transmitted signal and to have a reference point to start demodulation of the transmitted signals. Power line communication (PLC) systems, for example, have utilized reference preambles and OFDM signals for multi-carrier communications across power lines between transmitters and receivers.
Synchronization is typically required for the receiver to know the precise instant in time that the data arrives on the transmission medium. Typically, time domain correlation of a detected signal with respect to a known reference signal is utilized to synchronize a receiver to the transmitted signal. However, in the presence of interfering signals synchronization performance can be significantly degraded. In particular, impulsive noise and narrow band interference can result in poor synchronization performance for PLC receivers. These types of noise exceed what is typically seen in other communication environments, such as USB (universal serial bus) and RF communications. As such, PLC channels are particularly harsh environments for receiver synchronization.